Xylose acetal from

Andreesen JR, Schaupp A, Neurauter C, et al. 1973. Fermentation of glucose, fructose, and xylose by Clostridium thermoaceticum effect of metals on growth yield, enzymes, and synthesis of acetate from CO2. J Bacteriol 114 743-51. 

Ring opening of the cryptand derived from condensation of the branched tetraamine tren with 2,6-diacetylpyridine (in a 2 3 molar ratio) in the presence of manganese(II) acetate, NaBF4," " and NEts yielded the dinuclear complex Mn2L(CH3COO)](BF4)3 (where L = XH5) which was proposed as a structural model for active sites in natural systems. The Mn—Mn separation is 4.82 A compared with that of 4.9 A found in the D-xylose isomerase from Streptomyces rubiginosus. 

Microbial amino acids are mostly produced in Japan 6). The annual production of amino acids in Japan had reached a level of 300 million dollars in 197747). Microbial amino acids can be produced directly from intermediates or by enzymatic methods. A variety of substrates are used for microbial growth. These include molasses (especially beet), hydrolyzate, glucose, xylose, acetic acid, methanol, ethanol, benzoic acid, and n-paraflin. Investigations are being made in the search for inexpensive and easily available carbon sources 48). 

Recently, Bi et al. (2009) isolated En. asburiae JDR-1, a strain capable of fermenting both xylose and methylglucuronoxylose, which is released from hemicellulose upon acid treatment. The strain produced predominantly ethanol and acetate from hydrolysates of sweet gum xylan. To enhance ethanol production, the PET operon was introduced into En. asburiae JDR-1. Introduction of the PET operon led to homoethanol fermentation with acetate as a by-product. In addition, deletion of the native pfl gene enhanced ethanol production from xylan hydrolysates with 99% of theoretical yield and a rate of 0.11 g ethanol/L-h, which was 1.57 times the yield and 1.48 times the rate obtained with the ethanologenic strain E. coli KOI 1. 

D-Xylulose 5-phosphate (ii-threo-2-pentulose 5-phosphate, XP) stands as an important metabolite of the pentose phosphate pathway, which plays a key fimction in the cell and provides intermediates for biosynthetic pathways. The starting compound of the pathway is glucose 6-phosphate, but XP can also be formed by direct phosphorylation of D-xylulose with li-xylulokinase. Tritsch et al. [114] developed a radiometric test system for the measurement of D-xylulose kinase (XK) activity in crude cell extracts. Aliquots were spotted onto silica plates and developed in n-propyl alcohol-ethyl acetate-water (6 1 3 (v/v) to separate o-xylose/o-xylulose from XP. Silica was scraped off and determined by liquid scintillation. The conversion rate of [ " C]o-xylose into [ " C]o-xylulose 5-phosphate was calculated. Some of the works devoted to the separation of components necessary while analyzing enzyme activity are presented in Table 9.8. 

Selective removal of one isopropylidene group from a diacetal may be achieved by a variety of procedures, most of them involving protic or Lewis acids.100 Particularly common is the hydrolysis of the acetal engaging of the primary position of di-O-isopropylidene derivatives. Bhaskar et al,101 studied the selective deprotection of di-O-isopropylidene acetals derived from D-glucose, D-xylose, and D-mannose, using acid zeolites and montmorillonite K-10. When 102 was submitted to acid hydrolysis in aqueous methanol, the best yields (85—96%) for the monoacetal 105 were obtained when H-beta and HZSM-5 zeolites were employed as catalysts (Scheme 24, Table IV). HY zeolite proved to be ineffective, whereas the yield obtained for the montmorillonite K-10-catalyzed reaction was low (22%). The zeolites found most effective were then used for the hydrolysis of the diacetal 103 and 104, providing excellent yields for the desired corresponding monoacetals 106 and 107. 

Llangwell A process for making acetic acid by fermenting the cellulose in com cobs. Xylose is a co-product. The microorganism was isolated from the gut of the goat. Piloted on a large scale by the Commercial Solvents Company, Terre Haute, IN, from 1928 to 1930. 

Ross and Ugi" prepared l-amino-5-deoxy-5-thio-2,3,4-tri-6)-isobutanoyl-P-D-xylopyranose 61a from xylose via the 5-desoxy-5-thio-D-xylopyranose. The U-4CRs of this amine form a-aminoacid derivatives stereoselectively and in excellent yields. These products have the advantage that their products are stable and their auxiliary group 5-desoxy-5-thio-D-xylopyranose can be cleaved off selectively by mercury(II) acetate and trifluoroacetic acid. The expected steric structure of the corresponding U-4CR product was confirmed by X-ray measurement. 

D-Xylose and D-arabinose have been treated with a 0.5 M acetate buffer (pH 4.5) at reflux. Besides 2-furaldehyde, some catechols and unique chromones were isolated from the reaction mixture in small proportions. These included 3,8-dihydroxy-2-methylchromone and its precursor, 5,6,7,8-tetrahydro-3,5-dihydroxy-2-methyl-8-oxochromone. A trihydroxy-2-methylchromone was also isolated from the D-xylose reac-... 

Figure 3(A). Comparison of temperature optima for activities of glucose isomerase, amylase, and >galactosidase. Enzymes were assayed with cell extract from xylose-grown cells. A 100% activity value corresponds to 0.60, 0.58, and 0.46 U/mg for glucose isomerase, amylase, and -galactosidase, respectively. Cell extracts in 50 mM sodium phosphate buffer (pH 7.0), 100 mM sodium acetate buffer (pH 5.5), and 100 mM sodium phosphate buffer (pH 6.0) for glucose isomerase, amylase, and -galactosidase, respectively, were preincubatcd at the indicated temperatures, prior to the assay for residual enzyme activities. Reprinted with permission from ref. 20. Copyright 1990 American Society for Microbiology.

At the same time, in this laboratory, we detected the dimethyl acetals of D-xylose and D-glucose by chromatographic resolutions of the products of methanolsis of labelled free sugcirs, and we have, likewise, concluded that they are not primary products but are formed either concurrently with the furanosides or, more probably, from them 8). Fig. 3 illustrates the variations of the main components of the reaction of D-xylose as determined by radiochemical counting of the chromato-graphically resolved components (the pyranosides were vmresolved under the conditions used), and in Fig. 4 the concentration of the acetal is... 

After anomerisation and before initiation of the ring-expansion process, the a-and p-glucofuranosides were found to be present in a -equilibrium in the ratio 1 1.7 which agrees with the value obtained by radiochemical methods and with that observed by Bishop and Cooper for the methyl xylofuranosides 4). However, the ratio for the xylosides was found in the isotope work to be 1 1.2 (1 1.3 for ethyl xylofuranosides) regardless of whether they were derived from xylose or either of its methyl furanosides. A further relevant observation made with these furanosides was that acetal was formed during their anomerisation indicating that pathways (C) and (E) (Scheme 3) are open. 

D-Xylose. Maquenne obtained tetraacetyl-D-xylononitrile in 41% 3deld from the D-xylose employed, by treatment of the oxime with sodium acetate-acetic anhydride. From the nitrile, D-threose diacetamide was obtained in 30 % yield by the action of ammonia and it was hydrolyzed... 

The action of 1% methanolic hydrogen chloride on 1,2-O-iso-propylidene -3,5-di - O - p-tolylsulfonyl-D-xylofuranose (65) leads,81 after boiling for three hours under reflux, to 2,5-anhydro-3-0-p-tolylsulfonyl-D-xylose dimethyl acetal (66). The structure of 66 was demonstrated by conversion into the disulfonate 67 this was prepared independently from a 2,5-anhydro-D-xylose dialkyl dithio-acetal72 (48) by p-toluenesulfonylation followed by exchange of the acetal group in methanol in the presence of mercury salts. 

Apparently related to the two preceding reactions is the action of 2% methanolic hydrogen chloride on l,2-0-isopropylidene-5-seleno-a-D-xylofuranose (72) (obtained from the benzylseleno derivative, 71), which affords83 a mixture of 2,5-anhydro-5-seleno-D-xylose (and -D-lyxose) dimethyl acetal (73). Similarly, the action of the same reagent... 

Starting from the appropriate sulfonylated acetals 105, 106, and 107 (from 2,5-anhydro-D-ribose, -D-xylose, and -D-lyxose, respectively), the application of a method for elimination of vicinal, secondary disulfonates by reaction with sodium iodide in lV,IV-dimethylformamide in the presence of zinc112 has permitted"3 the preparation of the... 

DL-Dihydrostreptose and its ribo isomer were similarly obtained. Birch reduction of 2-methyl-3-furoic acid, followed by addition of methanol, bromination, and dehydrobromination, gave 402 as a mixture of the isomers. Hydroxylation of 402 with osmium tetraoxide-so-dium chlorate, and subsequent treatment with acetone-sulfuric acid afforded three isomeric acetals (403-405). The structures of these compounds were assigned on the basis of their H-n.m.r. spectra. In addition, the relationship between 403 and 404 was established by hydrolysis and reglycosidation. The methyl esters 403-405 were quantitatively reduced to the corresponding alcohols. The mixture of alcohols obtained from 403 and 404 was converted into crystalline 5-deoxy-3-C-(hydroxymethyl)-l,2-0-isopropylidene-a-DL-ribofuran-ose (406), which was compared directly with a sample prepared from D-xylose. Methyl 5-deox y-3-C-(hydroxy methyl)-2,3-O-isopropy lidene-/3-DL-lyxofuranoside (407), obtained by reduction of 405 with lithium aluminum hydride, was hydrolyzed with dilute hydrochloric acid, to give a,/3-DL-dihydrostreptose.2,ifi... 

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